6-Substituted-5,6-dihydro-a-pyrones

The second lead series of macrophage activation inhibitors was a family of novel 6-substituted 5,6-dihydro-a-pyrone esters found in fermentations of the fungal strain... 

Several related dihydro-a-pyrones occur in Goniothalamus species (see reference 115 for an extensive bibliography). Altholactone (114) is such a bicyclic compound while compounds (115-118) with a [3.3.11-structure are the products of Michael-type cyclizations involving the 2 -OH and the oc,P-unsaturated lactone of the 6-substituted 5,6-dihydro-a-pyrone precursor. The structures and relative configurations of goniopyrone (115) and 5-deoxygoniopyrone (116) were deduced by ... 

Davies-Coleman, M.T., and D.E.A. Rivett Naturally Occurring 6-Substituted 5,6-dihydro-a-pyrones. Fortschr. Chem. organ. Naturstoffe, 55, 1 (1989). 

Sehlapelo, B.M., S.E. Drewes, and R. Scott-Shaw A 6-Substituted 5,6-Dihydro-a-pyrone from Two Species of Cryptocarya. Phytochem., 37, 847 (1994). 

Contents M.T. Davies-Coleman and D. E. A. Rivett Naturally Occurring 6-substituted 5,6-dihydro-a-pyrones -K. Krohn Building Blocks for the Total Synthesis of Anthracyclinones - M. Lounasmaa and J. Galambos Indole Alkaloid Production in Catharanthus Roseus Cell Suspension Cultures -C. E. James, L. Hough, and R. Khan Sucrose and Its Derivatives. 

Lia DJ, Mariko K, Hiromitsu T, Sjamsul AA, Norio A. A 6-substituted-5,6-dihydro-2-pyrone from Cryptocarya strictifolia. Phytochemistry 2000 54 989-993. 

Shao L, Kawano H, Sahuri M, Uchida Y. Asymmetric hydrogenation of 3,5-dioxoesters catalyzed by Ru-binap complex a short step asymmetric synthesis of 6-substituted 5,6-dihydro-2-pyrones. Tetrahedron 1993 49 (10) 1997-2010. 

Dihydro-a-pyrones substituted at C-6, also called a,p-unsaturated 5-lactones (Fig. 16), are bioactive phytochemicals produced by some plant species their versatile therapeutic effects have been associated with the presence of the a,p-unsaturated 8-lactone moiety. 

Related to this methodology is another one recently developed by Kirsch et al. [61], in which (Z)-aUylic alcohols are first converted into their trichloroacetimidates, and the latter are then subjected to a catalytic Sj 2 substitution of the trichloroace-timidate by a carboxylate group under the influence of complex 132, available in both enantiomeric forms (Scheme 2.26). If a p,y-unsaturated acid is used, an allyl P,y-unsaturated ester is obtained, which, after RCM and base-catalyzed migration of the double bond, affords a 5,6-dihydro-a-pyrone. The authors demonstrated the practical applicabihty of this methodology with the synthesis of (-)-rugulactone and other natural products. 

Propionic acid, 2-iodo-3-nitro-, ethyl ester [Propanoic acid, 2-iodo-3-mtro-, ethyl ester], 65 2//-Pyran, 3,4-dihydro-, 51 2//-PYR AN-2-ONE, 49 2H Pyran 2-one, 5 bromo 5,6-dihydro, 50 27/-PYRAN-2-ONE, 5,6 DIHYDRO-, 49 PYRIDINE, 2,3,4,5 TETRAHYDRO, 118 Pyridines, -substituted, 34 a Pyrone-6-carboxyhc acid [2H Pyran-6-Larboxyhc acid 2-oxo ], 51 Pyrroles, 34... 

Substituted derivatives of 5,6-dihydro-a-pyrones (dihydropyran-2-ones or more specifically 2H-dihydropyran-2-ones) occur widely in nature, particularly in plants and bacteria. They possess an a,P-unsaturated-5-lactone ring (1) with an alkyl, alkenyl or aryl substituent at C-6 and occasionally a varied substitution pattern around the ring. Many of these compounds are biologically active, exhibiting phytotoxi-... 

In addition to the considerable variety of methods for the synthesis of non-fluorinated y-pyrones [2], Tyvorskii and co-workers have described three new procedures, which produced 2-(perfluoroalkyl)-4-pyrones. One of them is a convenient two-step synthesis of 5-substituted 2-(perfluoroalkyl)-4 f-pyran-4-ones 2 by dehydration of 2,3-dihydro-3-hydroxy-6-(perfluoroalkyl)-4 f-pyran-4-ones 1 prepared... 

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